Wireless devices, such as cell phones and vehicle telematics units, carry out voice and data communications with third parties. These communications often involve wirelessly sending packetized data through a wireless carrier system. As part of communicating this way, both the wireless device as well as the third party each may use a distinct IP address so that the communications between them are routed appropriately. To set up a communication session between the wireless device and the third party, the entity setting up the session (whether it is the device or the third party) must know the IP address of the other entity in order to communicate data. However, the IP addresses of wireless devices may not be accessible by third parties that want to send wireless devices packetized data. A benefit of this arrangement is that unwanted mobile-terminated packet data connections can be prevented because the IP addresses of the wireless/mobile devices are not available to malicious third parties. But this scheme also prevents legitimate mobile-terminated packet data connections placed by trusted third parties as well.